Heat and energy exchange

ABSTRACT

Materials, components, and methods are provided that are directed to the fabrication and use of micro-scale channels with a fluid for a heat exchange system, where the temperature and flow of the fluid is controlled, in part, through the macroscopic geometry of the micro-scale channel and the configuration of at least a portion of the wall of the micro-scale channel and the constituent particles that make up the fluid. Moreover, the wall of the micro-scale channel and the constituent particles are configured such that collisions between the constituent particles and the wall are substantially specular. Accelerating and decelerating elements provided herein can be configured with micro-scale channels which can trace out a generally spiral path.

DESCRIPTION

This application claims priority to U.S. Provisional Application No.61/347,446, filed May 23, 2010, the contents of which are incorporatedherein by reference. This application is related to co-pending U.S.application Ser. No. 12/585,981, filed Sep. 30, 2009, the contents ofwhich are incorporated by reference, and which itself claims the benefitof U.S. Provisional Application No. 61/101,227, filed Sep. 30, 2008.

FIELD

Materials, components, and methods consistent with the presentdisclosure are directed to the fabrication and use of micro-scalechannels with a fluid, where the micro-scale channels are arrangedaccording to certain macroscopic configurations so as to at leastpartially control the temperature and flow of the fluid.

BACKGROUND

A volume of fluid, such as air, can be characterized by a temperatureand pressure. When considered as a collection of constituent particles,comprising, for example, molecules of oxygen and nitrogen, the volume offluid at a given temperature can also be characterized as a distributionof constituent particle speeds. This distribution can be characterized,generally, by an average speed which is understood to bear arelationship with the temperature of the fluid (as a gas, for example).

Accordingly, the internal thermal energy of a fluid can provide a sourceof energy for applications related to heating, cooling, and thegeneration of fluid flow.

SUMMARY

In one aspect, embodiments can provide a system that utilizes one ormore micro-scale channels (a “micro channel”) configured to accommodatethe flow of a fluid, and where the walls of the micro channel and theconstituent particles in the fluid are configured such that collisionsbetween the constituent particles and the walls of the micro channel aresubstantially specular. Moreover the micro channel can be arranged in amacroscopic configuration to provide at least one wall with at least afirst wall portion that is at least approximately planar, a second wallportion that is at least approximately planar, a third wall portion thatis approximately planar, a first intermediate wall portion, and a secondintermediate wall portion, where a boundary of the first wall portion iscontiguous with a first boundary of the first intermediate wall portion,a first boundary of the second wall portion is contiguous with a secondboundary of the first intermediate wall portion, a second boundary ofthe second wall portion is contiguous with a first boundary of thesecond intermediate wall portion, and a boundary of the third wallportion is contiguous with a second boundary of the second intermediatewall portion, such that the first wall portion, the first intermediatewall portion, the second wall portion, the second intermediate wallportion, and the third wall portion form a contiguous wall of a portionof the micro channel. Further still, embodiments can provide that afirst normal to the approximate plane defined by the first wall portionis not parallel to a second normal to the approximate plane defined bythe second wall portion, and is also not parallel to a third normal tothe approximate plane defined by the third wall portion, and where thesecond normal is also not parallel to the third normal. Further still,embodiments can provide that the angle offset between the first normaland the second normal is less than 90 degrees, and is approximately thesame as the angle offset between the second normal and the third normal.Where the separation between the first wall portion and the second wallportion is at least N times the largest width of the micro channel overthat separation (where N can be an integer), the angle offset betweenthe first normal and the second normal can be less than N/10 degrees.Likewise, where the separation between the second wall portion and thethird wall portion is at least N times the largest width of the microchannel over that separation, the angle offset between the second normaland the third normal can be less than N/10 degrees. For example purposesonly, where the separation between the first wall portion and the secondwall portion (and the separation between the second wall portion and thethird wall portion) is at least twenty-five times the largest width ofthe micro channel over that separation, the angle offset between thefirst normal and the second normal (and the second normal and the thirdnormal) can be less than 2.5 degrees. Likewise, for example purposesonly, where the separation between the first wall portion and the secondwall portion is at least fifty times the largest width of the microchannel over that separation, the angle offset between the first normaland the second normal can be less than 5 degrees.

In another aspect, embodiments can provide for the the manipulation offlow and temperature of a volume of fluid, where the fluid can comprisemolecules, and can allow for the population of molecular vibrationallevels through enhanced heating of a volume of the fluid. Where suchvibrationally-excited molecules are allowed to relax, embodiments canallow for the creation and manipulation of electromagnetic radiationemitted thereby.

In a further aspect, embodiments can provide for the manipulation offlow and temperature of a volume of fluid, and can provide for practicalapplications ranging from heating and cooling, refrigeration,electricity generation, coherent and non-coherent light emission, gaspumping, plasma and particle beam production, particle beamacceleration, chemical processes, and others.

Additional objects and advantages of the disclosure will be set forth inpart in the description which follows, and in part will be obvious fromthe description, or may be learned by practice of embodiments consistentwith the disclosure. The objects and advantages can be realized andattained by means of the elements and combinations particularly pointedout in the appended claims.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the invention, as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate an embodiment of the disclosureand together with the description, serve to explain the principles ofthe disclosure.

FIG. 1 depicts an exemplary heat exchange system consistent with thepresent disclosure;

FIG. 2 is an exemplary view of the micro channels within an acceleratingelement of the system of FIG. 1;

FIG. 3 is an exemplary illustration of a specular collision consistentwith the present disclosure;

FIG. 4 is an exemplary view of the micro channels within a deceleratingelement of the system of FIG. 1;

FIG. 5 depicts an exemplary view of an interface and a connectionchannel connecting an accelerating element and a decelerating element ofthe system of FIG. 1; and

FIG. 6 depicts exemplary normal vectors to the walls of the microchannels and the angular offsets within an accelerating element of thesystem of FIG. 1.

DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to the present embodiment(exemplary embodiment) of the disclosure, characteristics of which areillustrated in the accompanying drawings. Wherever possible, the samereference numbers will be used throughout the drawings to refer to thesame or like parts.

FIG. 1 depicts a view of exemplary heat exchange system 100 consistentwith the present disclosure. Pump 150 is configured to generate and/ormaintain a flow of fluid (such as air, for example) from channel 152 tochannel 151. Arrow 118 indicates an exemplary fluid flow into channel151, and arrow 128 indicates an exemplary fluid flow from channel 152.

In general, consistent with the present disclosure, sub-system 110 caninclude a plurality of accelerating elements 115, where eachaccelerating element 115 includes micro channels (to be describedfurther below) in fluid communication with channel 151. Further,sub-system 120 can include a plurality of decelerating elements 125,where each decelerating element 125 also includes micro channels (to bedescribed further below) in fluid communication with channel 152.Further still, consistent with an exemplary embodiment of the presentdisclosure, there can be a one-to-one correspondence between each ofmicro channel of each accelerating element 115 and each of micro channelof each decelerating element 125, where the one-to-one correspondencecan be realized by ensuring that the micro channel of each acceleratingelement 115 is in fluid communication with a micro channel of adecelerating element 125 through interface 130.

In a preferred embodiment, each pair of accelerating element 115 anddecelerating element 125 can transfer 100 watts from the cold side(accelerating element 115) to the hot side (decelerating element 125).The dimensions of such an accelerating element 115 within such a 100watt pair of accelerating and decelerating elements can be 100millimeters by 100 millimeters. In a further embodiment, an additionalheat exchange element (not shown) may be affixed to each acceleratingelement 115 and decelerating element 125. In an embodiment consistentwith the disclosure, the additional heat exchange element can besubstantially planar (such as accelerating element 115 and deceleratingelement 125 are planar) and serve to conduct heat away from deceleratingelement 125 into the ambient air (by providing additional surface areato dissipate such energy) or serve to conduct heat to acceleratingelement 115 from the ambient air (again, by providing provide additionalsurface area for cooling purposes). The additional heat exchange elementcan be 100 millimeters by 100 millimeters, thereby making the dimensionsof the combined accelerating element 115 and additional heat exchangeelement 100 millimeters by 200 millimeters, and making the dimensions ofthe combined decelerating element 125 and additional heat exchangeelement 100 millimeters by 200 millimeters in one embodiment. In theembodiment depicted in FIG. 1, with twenty (20) such pairs ofaccelerating element 115 and decelerating element 125 depicted, system100 can be capable of transferring 2 kilowatts from sub-system 110 tosub-system 120. In a further preferred embodiment, with 35 such pairscapable of transferring 3.5 kilowatts from a cold side to a hot side,the height, H, of a 3.5 kilowatt system can be approximately 300millimeters. Where interface 130 is 10 millimeters wide (and taking intoaccount the additional heat exchange elements described above), theoverall dimensions of such a 3.5 kilowatt system can be 300 millimetersby 210 millimeters by 200 millimeters. Further, the exemplary diameterof channel 151 and channel 152 can be 25 millimeters or more.Furthermore, in such an exemplary 3.5 kilowatt system, where the fluidis air, pump 150 can be a 300-500 watt air pump. Further still, in suchan exemplary embodiment, the air to be circulated through system 100 canbe drawn from the immediate environment of system 100.

Channel 151 is in fluid communication with channel 152 through aplurality of micro channels within the plurality of acceleratingelements 115, interface 130, and decelerating elements 125. Arrow 138depicts the flow of fluid from accelerating element 115 to deceleratingelement 125 through interface 130.

FIG. 2 is a schematic view of micro channel 210 within an exemplaryaccelerating element 115 of FIG. 1. Channel 151 is depicted as anopening in accelerating element 115, and in fluid communication withmicro channel 210. The scale of micro channel 210 as depicted in FIG. 2is for illustration purposes. Micro channel 210 can be engineered to besmall (i.e., with an internal surface area that may be as small asapproximately 3e-11 m̂2 per linear micron to 6e-10 m̂2 per linear micronin a preferred embodiment, which can correspond, respectively, to achannel with an approximate diameter of 9 microns to 180 microns). Asdepicted in FIG. 2 in an exemplary embodiment, micro channel 210 isapproximately confined to a planar region (i.e., accelerating element115) and exhibits a spiral such that a fluid entering from channel 151enters micro channel 210, describing arcs of increasing radius until thefluid enters entering linear channel 220. In a preferred embodiment, thetotal length of micro channel 210 from channel 151 until reaching linearchannel 220 can be approximately 10 mm to more than 1 meter. Furtherstill, as discussed above, in a preferred embodiment where acceleratingelement 115 is one of a 100 watt pair of accelerating and deceleratingelements, the width W can be 100 millimeters.

Furthermore, in a preferred embodiment, the walls of micro channel 210can be substantially specular, FIG. 3 depicts a portion of FIG. 2 inmore detail. Specifically, arrow 325 represents a velocity component ofconstituent particle 310 before constituent particle 310 collides withwall 305. (Wall 305 is an enlarged view of an exemplary wall of microchannel 210, and constituent particle 310 corresponds to a constituentparticle in an exemplary fluid flowing through micro channel 210according to a preferred embodiment.) Normal 306 represents an axis thatis perpendicular to the plane defined by wall 305. Arrow 335 representsa velocity component of constituent particle 310 after constituentparticle 310 collides with wall 305. As used herein, a specularcollision between constituent particle 310 and wall 305 is a collisionin which the velocity component of constituent particle 310 parallel toplane 302 determined by local portion 301 of wall 305 proximal to thecollision between constituent particle 310 and wall 305, issubstantially the same before and after the collision. Moreover, duringa specular collision, the speed of constituent particle 310 associatedwith the velocity component perpendicular to the plane of wall 305 canbe substantially the same before and after the collision. One skilled inthe art should appreciate that the term “specular collision” as usedherein should not be interpreted to apply to elastic collisions only.Rather, because there can be a transfer of energy (on the average)between wall 305 of the micro channel and a plurality constituentparticles 310, it is understood that any one particular specularcollision between constituent particle 310 and wall 305 can increase ordecrease the kinetic energy of constituent particle 310 relative to thekinetic energy it possessed prior to the collision. For example, ifthere is a transfer of energy from wall 305 to constituent particle 310,then one would expect that the acute angle between constituent particle310 and the plane parallel to wall 305 would be larger after thecollision than before the collision. Likewise, if there is a transfer ofenergy from constituent particle 310 to wall 305, then one would expectthat the acute angle between constituent particle 310 and the planeparallel to wall 305 would be smaller after the collision than beforethe collision. Furthermore, where the temperature of the fluidcomprising a plurality of constituent particles is different from thetemperature of the wall, there can be a transfer of internal energy fromthe fluid to the wall, or from the wall to the fluid (depending uponwhich is at the higher temperature). Where the collisions between aplurality of constituent particles 310 and wall 305 are substantiallyspecular as used herein, a transfer of energy from a fluid flowingthrough micro channel 210 to wall 305 or from wall 305 to the fluidflowing through micro channel 210 can occur predominantly through theaverage change in the speed of constituent particle 310 associated withthe change in its velocity component perpendicular to the plane of wall305 during the collision. One should also appreciate that such a changein the velocity component of constituent particle 310 during thecollision can change the overall speed of constituent particle 310 as aresult of the collision process.

In an embodiment consistent with the present disclosure, the surface ofthe walls of micro channel 210 can include any suitable materialconfigured for specular collisions, such as silicon, tungsten, gold,platinum, and diamond. Such a surface may be deposited onto microchannel 210 using any of a variety of MEMs fabrication techniques,including, but not limited to, sputtering and evaporative deposition.Furthermore, consistent with the present disclosure, diamond smoothfilms with grains as small as 100 nm and 20 nm Ra roughness can be grownonto channel walls. In one embodiment, diamond can be preferable as aresult of its melting point (i.e., approx. 4000 K at one atmosphere) andas a result of its hardness (i.e., a10 in Mohs scale for hardness).Consistent with further embodiments of the present disclosure, thesurface of the walls of micro channel 210 can also include tungstencarbide, glass and pyrolytic graphite—in part at least because of itshigh thermal conductivity of 1700 W/mK. Micro channel 210 can alsoinclude a diamond nanoparticle film on pyrolytic graphite substrate.

FIG. 4 is a schematic view of micro channel 410 within an exemplarydecelerating element 125 of FIG. 1. Channel 152 is depicted as anopening in decelerating element 125, and in fluid communication withmicro channel 410. Again, the scale of micro channel 410 as depicted inFIG. 4 is for illustration purposes. Micro channel 410 can be engineeredto be small (i.e., with an internal surface area that may be as small asapproximately 3e-11 m̂2 per linear micron to 6e-10 m̂2 per linear micronin a preferred embodiment, which can correspond, respectively, to achannel with an approximate diameter of 9 microns to 180 microns). Asdepicted in FIG. 4 in an exemplary embodiment, micro channel 410 isapproximately confined to a planar region (i.e., accelerating element125) and exhibits a spiral such that a fluid entering from linearchannel 420 enters micro channel 410, describing arcs of decreasingradius until the fluid enters entering channel 152. In a preferredembodiment, the total length of micro channel 410 from linear channel420 until reaching channel 152 can be approximately 10 mm to more than 1meter. Further still, as discussed above, in a preferred embodimentwhere decelerating element 125 is one of a 100 watt pair of acceleratingand decelerating elements, the width W can be 100 millimeters.Furthermore, in a preferred embodiment, the walls of micro channel 410can be substantially specular.

In an embodiment consistent with the present disclosure, the surface ofthe walls of micro channel 410 can include any suitable materialconfigured for specular collisions, such as silicon, tungsten, gold,platinum, and diamond. Such a surface may be deposited onto microchannel 410 using any of a variety of MEMs fabrication techniques,including, but not limited to, sputtering and evaporative deposition.Furthermore, consistent with the present disclosure, diamond smoothfilms with grains as small as 100 nm and 20nm Ra roughness can be grownonto channel walls. In one embodiment, diamond can be preferable as aresult of its melting point (i.e., approx. 4000 K at one atmosphere) andas a result of its hardness (i.e., a10 in Mohs scale for hardness).Consistent with further embodiments of the present disclosure, thesurface of the walls of micro channel 410 can also include tungstencarbide, glass and pyrolytic graphite—in part at least because of itshigh thermal conductivity of 1700 W/mK. Micro channel 410 can alsoinclude a diamond nanoparticle film on pyrolytic graphite substrate

FIG. 5 depicts connection 510 between linear channel 220 and linearchannel 420 through interface 130.

In a preferred embodiment, where the fluid is air, channel 151 can bekept at a relatively high pressure, and channel 152 can be kept at arelatively low pressure, so as to allow for the flow of fluid throughthe plurality of accelerating elements 115 and decelerating elements125. In a preferred embodiment, the channel 151 can exhibit a pressureof approximately 1 atm or more, and channel 152 can exhibit a pressurethat is approximately 0.528 of the pressure of channel 151.

Turning to FIG. 6, which depicts an expanded view of micro channel 210,fluid that is at the inner portion of micro channel 210 (i.e., proximalto inflow opening 601) can be induced to flow through spirals ofincreasing radii through the use of a pressure differential as discussedabove. Where the temperature of the fluid at inflow opening 601 is T₁,then the constituent particles (such as constituent particle 310 in FIG.3) can be represented by a distribution of speeds, the average speed ofwhich is proportional to temperature.

Where the throat of inflow opening 601 is small (for example, anywherefrom 0.01 μm̂2 to 500 μm̂2 where the fluid is air), then the constituentparticles of a fluid moving through inflow opening 601 into microchannel 210 can exhibit a velocity that has its component parallel todirection 650 larger than its component perpendicular to direction 650.Consequently, the fluid passing through micro channel 210 acquires aflow velocity that is predominantly parallel to direction 650. Thekinetic energy that is associated with the flow of fluid in direction650 is drawn from the internal thermal energy of fluid, which was at T₁before it entered inflow opening 601. Conservation of energy dictatesthat, because a portion of the original thermal energy of fluid at T₁has been converted to kinetic energy of flow for fluid passing throughmicro channel 210, the temperature of fluid (in a frame that isstationary with the velocity of flow) in micro channel 210 can be lowerthan T₁, which we will designate as T₂. Where T₂ is also less than thetemperature of wall 610 (which we will designate as T_(w)) of microchannel 210, then the fluid in micro channel 210 can cool the materialcomprising accelerating element 115.

Micro channel 210, consistent with an embodiment of the presentdisclosure is configured to enhance the effect this temperature changehas on the fluid passing through micro channel 210 in at least threeways. Specifically, where wall 610 and the constituent particles in thefluid are configured such that collisions between wall 610 and theconstituent particles are substantially specular, then suchcollisions—which are a means of transferring energy between wall 610 andthe fluid—will have a minimal effect on the overall flow of fluidthrough micro channel 210. In other words, where the collision betweenthe constituent particle and wall 610 is such that the velocity of theconstituent particle is equally likely to be in any direction away fromwall 610 (i.e., a non-specular collision), then a plurality of suchcollisions will have the effect of slowing down the flow of the fluid,which will also likely have the effect of raising the internaltemperature of the fluid in micro channel 210. Micro channel 210,consistent with an embodiment of the present disclosure, is configuredto enhance the effect of cooling by selectively avoiding the effect ofnon-specular collisions.

In addition, because the outer wall of micro channel 210 is configuredas a generally increasing spiral, the specular scattering of aconstituent particle off of successive portions of the wall of microchannel 210 (such as portions 610, 615, and 620), can convert a portionof the velocity component which was perpendicular to the direction offlow through micro channel 210 (i.e., a radial velocity component) to acomponent parallel to the direction of flow through micro channel 210.Because the spiral grows larger along the path of micro channel 210, theconstituent particles can undergo less and less collisions with the wall(along the path of micro channel 210) as the fluid travels towardslinear channel 220.

Moreover, because micro channel 210 is engineered to be small (i.e.,with an internal surface area that may be as small as approximately3e-11 m̂2 per linear micron to 6e-10 m̂2 per linear micro in a preferredembodiment), then the ratio of the surface area presented by the wall ofmicro channel 210 to a given volume of fluid in any region within microchannel 210 is relatively large (i.e., where the volume of the fluidenclosed by the above surface is approximately 8e-17 m̂3 per linearmicron to 3e-15 m̂3 per linear micron). Because the surface areapresented by the wall of micro channel 210 to a volume of fluid is aprimary means of energy exchange between the walls and the fluid 115,this can tend to maximize the overall energy exchange interactionbetween the fluid and micro channel 210.

For example, as shown in FIG. 6, a constituent particle can enter inflowopening 601 with a component predominantly parallel to direction 650,and undergoes a specular collision with local region 610 of the wall ofmicro channel 210, and acquires a velocity component in direction 651.The constituent particle may now undergo a specular collision with localregion 615 of the wall of micro channel 210, and acquires a velocitycomponent in direction 652. The constituent particle can undergo aspecular collision with local region 620 of the wall of micro channel210, and acquire a further velocity component along the generaldirection of micro channel 210.

Angle β corresponds to the angular offset between normal 625 and normal630. Angle α corresponds to the angular offset between normal 630 andnormal 635. In a preferred embodiment, where the separation between thefirst wall portion and the second wall portion is at least N times thelargest width of the micro channel over that separation (where N can bean integer), the angle offset between the first normal and the secondnormal can be less than N/10 degrees. Likewise, where the separationbetween the second wall portion and the third wall portion is at least Ntimes the largest width of the micro channel over that separation, theangle offset between the second normal and the third normal can be lessthan N/10 degrees. For example, preferably where the separation betweenthe first wall portion and the second wall portion (and the separationbetween the second wall portion and the third wall portion) is at leasttwenty-five times the largest width of the micro channel over thatseparation, the angle offset between the first normal and the secondnormal (and the second normal and the third normal) is less than 2.5degrees. Likewise, preferably where the separation between the localregion 610 and local region 615 is at least fifty times the largestwidth of micro channel 210 over that separation, the angle offsetbetween normal 625 and normal 630 can be less than 5 degrees. Similarly,where the separation between local region 615 and local region 620 is atleast fifty times the largest width of micro channel 210 over thatseparation, the angle offset between normal 630 and normal 635 can beless than 5 degrees.

In this manner, accelerating element 115 can be cooled by the passage ofa fluid, where the fluid is configured to exhibit specular collisionswith the walls of micro channel 210. Moreover, a fluid passing throughaccelerating element 115 can be accelerated: i.e., when the fluidarrives at linear channel 220, the velocity components of the fluid'sconstituent particles are predominantly along the direction of linearchannel 220 leading to connection 510.

Recapping somewhat, and consistent with the present disclosure, thetranslational kinetic energy (TKE) of the constituent particles in afluid (i.e., molecules in a molecular beam) can be reduced by collisionswith a surface. The percentage of TKE transferred from the fluid to thesurface can be dependent upon the velocity of the fluid, the smoothnessof the surface, the internal kinetic energy of the constituent particlesin the fluid and the kinetic energy density of the surface.

A fluid (as a molecular beam) with a particular root mean square (RMS)velocity and a constant average angle of incidence can transfer moreenergy to a smooth surface with a lower kinetic energy density than tothe same surface when it is placed at a higher energy density. If theenergy density of the surface is sufficiently high with respect to theenergy density of an impinging molecular beam no energy will betransferred from the beam to the surface.

Surface collisions that result in a net energy transfer to the surfacecan reduce the internal kinetic energy level of constituent particles inthe fluid. When the internal energy level of a molecule has been reducedsufficiently (such as through vibrational energy levels) it can emit oneor more photons at a frequency that is commensurate with the reducedinternal energy level.

The same principle of operation can apply to decelerating element 125,where micro channel 410 is configured as a spiral that presentssuccessively smaller radii to a fluid passing from linear channel 420 tochannel 152. In this manner, a high velocity fluid arriving fromconnection 510 to linear channel 420 can undergo more and morecollisions with the wall (along the path of micro channel 210) as thefluid travels towards channel 152.

As with accelerating element 115 and micro channel 210, the walls ofmicro channel 410 in decelerating element 125 are configured to causethe constituent particles in the fluid passing through micro channel 410to undergo specular collisions.

In addition, where the constituent particles of the fluid are molecules(and, for example, where the fluid is a gas), then certain vibrationalstates of the constituent particles may be populated as a result of theincrease in temperature that is achieved near the inner opening betweenmicro channel 410 and channel 152.

Consistent with the present disclosure, a molecular beam in a MEMSdevice (such as accelerating element 115 and decelerating element 125)that can be used for cooling electronics, refrigeration, airconditioning and other applications can exhibit high RMS velocities. Amolecular beam composed of room air with an RMS velocity of 2,000 metersper second has the translational kinetic energy of still air at over4,000 K, a temperature that is well beyond the melting point of mostmaterials. A refrigeration system's hot-side heat exchanger preferablywould have the ability to extract precise quantities of bothtranslational and internal kinetic energy from the accelerated molecularbeam without damage to a heat exchanger composed of conventionalmaterials, such as aluminum and thermally conductive plastics with amelting point of only 933 K or less.

A gradual reduction in the translational kinetic energy level of a fastmolecular beam with a high energy density relative to that of thesurface allows for energy transfer to the surface to occur over anextended surface length. This is a desirable method of extracting theenergy from a molecular beam when a more concentrated extraction woulddamage the channel or raise the temperature of a device beyond practicallimits. With this gradual energy extraction approach, a hot side heatexchanger in a refrigeration system that is made of aluminum with amelting point of 933 K can be used to transfer extracted energy from ahigh energy molecular beam with an RMS velocity of 2,000 m/s or more tothe outside environment without damaging the channels of the heatexchange device and not overheating any portion of the outer surface ofthe heat exchanger device. With a gradual kinetic energy extractionmethodology, virtually any conformal channel material including ceramicsand thermally conductive polymers can be used as channels and thermalpackaging in hot-side heat exchanger applications.

As described herein, when a molecular beam experiences a series ofsurface collisions with an arc of gradually decreasing radius,translational and internal kinetic energy is extracted gradually. Avariety of MEMS device channel designs can permit a molecular beam toexperience such a series of collisions with an arc of graduallydecreasing radius. For example, channels configured as spirals with aninitially large radii that gradually reduce over length to a smallerradii, and a spiraling molecular beam progressing through an attenuatedchannel using the centrifugal force of the spiral motion to remain inclose proximity to the surface at all diameters of the channel are twoexamples of such designs. Any gradual energy extraction design wouldserve to facilitate the conversion of the beams kinetic energy toinfrared and optical wavelengths of light even when the average energycontent of the beam, if abruptly slowed or stopped could produce higherfrequency emissions. For applications requiring higher frequencyemissions, designs that facilitate more abrupt energy extraction methodscan of course be applied and are within the scope of this disclosure.

An equation describing the approximate transfer of energy from thetranslational energy of a molecular beam to a collision surfacetemperature can be derived through kinetic theory. In the equation(3kT)/2=(mv̂2)/2, k is Boltzmann's Constant, T is temperature in Kelvins,m is mass and v is velocity. Because energy increases with the square ofthe velocity, the quantity of kinetic energy that can be transferred toa surface by slowing a faster beam by one meter per second can be morethan the quantity that can be transferred to the same surface by aslower molecular beam with the same reduction in velocity. The localtemperature of the collision surfaces and thermal path that extends tothe outer surfaces can be controlled with complementary collision angleswith known velocity ranges of a molecular beam.

A heat exchanger consistent with the present disclosure that graduallyabsorbs the kinetic energy from a high energy molecular beam can beheated as kinetic energy from the molecular beam is absorbed by the heatexchanger's inner channel surfaces. Provided that there is asufficiently conductive thermal path between the inner channel surfacesand the outer surfaces of the heat exchanger, the heat exchanger andmolecular beam channel surfaces can be maintained with any desired deltaT (change in temperature) with the ambient surroundings withconventional means of heat transfer from the heat exchanger to theambient environment. Heat exchangers that evenly extract energy from amolecular beam along a channel surface can very nearly approximatenearly isothermal conditions.

Energy extracted from an equilibrated molecular beam can be used toprecisely quantize the modes of energy in a channel cavity. Emissions oflight with a predictable energy are provided by Plank's radiationformula that is equal to Planck's constant times the frequency. Plank'sradiation formula can be used to calculate the average energy of anydesired frequency of light emitted from a MEMS device channel.

Continuous coherent spontaneous emission can also occur when acollimated and equilibrated molecular beam transfers highly resolvedquantities of energy to the surface of a channel. Channel transparencyto the emitted frequency of light can allow for the light to escape thechannel for practical purposes that include any laser application andconversion of light energy to electric current as would occur by aphotodiode array in the flux path of the photonic emissions from thechannels. The voltage of the current can be related to the bandgapenergy of the channel material. Coherent emissions can permitphotodiodes with a narrow bandwidth to efficiently convert extractedenergy from a molecular beam to an electric current of a desiredvoltage.

Coherent and in-phase emissions from several channels can be readilyachieved from a series of parallel channel surfaces on a MEMS deviceusing ultra-flat wafer surfaces. Energy density of coherent emissionscan be accomplished with sub-micron gaps between parallel channels. MEMSdevices with optically and UV transparent channels with excellentoptical homogeneity can be fabricated using a variety of materials.Silicon can provide suitable transparent optical homogeneity to someinfrared frequencies, as can germanium and Amtir. Sapphire, yttria, andyttrium alumina garnet provide excellent optical transmission ofinfrared as well. Optical glass can be used for UV and opticalwavelengths.

In a preferred embodiment, the architecture or micro channel 210 andmicro channel 410 can reduce pumping power requirements. Due at least inpart to such architecture, the values associated with the coefficient ofperformance (“COP”) can be 10 or higher.

In a further embodiment consistent with this disclosure, values of COPcan be 10 or higher by operating at different pressures. For example, inan exemplary embodiment, the power required per constituent particle (ormolecule) is a function of the pressure ratio, and not the pressure. Forexemplary systems 100 that operate at higher pressures, but that areconfigured to exhibit the same pressure ratio, a pumping cost perconstituent particle will remain the same, but a higher density flow ifconstituent particles (i.e., a higher density molecular beam) canprovide higher heat transfer rates and could produce a COP of 10 ormore.

Materials and components consistent with the present disclosure, such asthe exemplary devices described above, offers solutions to all of theproblems that have been identified

Other embodiments consistent with the disclosure will be apparent tothose skilled in the art from consideration of the specification andpractice of the embodiments disclosed herein. It is intended that thespecification and examples be considered as exemplary only, with a truescope and spirit of the invention being indicated by the followingclaims.

1-70. (canceled)
 71. An apparatus for heat exchange comprising: a microchannel comprising a wall portion; and a gas comprising a constituentparticle; wherein the micro channel is configured to accommodate a flowof the gas in a first direction substantially perpendicular to a crosssection of the micro channel; and wherein the wall portion and theconstituent particle are configured such that collisions between theconstituent particle and the wall portion are substantially specular;and wherein the wall portion comprises at least a first wall portion, asecond wall portion, a third wall portion, a first intermediate wallportion, and a second intermediate wall portion; wherein a boundary ofthe first wall portion is contiguous with a first boundary of the firstintermediate wall portion, a first boundary of the second wall portionis contiguous with a second boundary of the first intermediate wallportion, a second boundary of the second wall portion is contiguous witha first boundary of the second intermediate wall portion, and a boundaryof the third wall portion is contiguous with a second boundary of thesecond intermediate wall portion, such that the first wall portion, thefirst intermediate wall portion, the second wall portion, the secondintermediate wall portion, and the third wall portion form a contiguousportion of the wall of the micro channel; wherein a first normal to thefirst wall portion is not parallel to a second normal to the second wallportion, and is also not parallel to a third normal to the third wallportion, and where the second normal is also not parallel to the thirdnormal; wherein an angle offset between the first normal and the secondnormal is less than 90 degrees, and is approximately the same as anangle offset between the second normal and the third normal; wherein aseparation between the first wall portion and the second wall portion isat least an integer N times a largest width of the micro channel overthat separation; and wherein the angle offset between the first normaland the second normal is less than M degrees where M equals N/10. 72.The apparatus of claim 71, wherein N is selected from at least one of:twenty-five and fifty.
 73. The apparatus of claim 71, wherein the gascomprises air.
 74. The apparatus of claim 71, wherein the micro channelis substantially confined to a planar region.
 75. The apparatus of claim71, wherein a path of the micro channel is a spiral with an innerportion and an outer portion, wherein a radius if the outer portion isgreater than a radius of the inner portion.
 76. The apparatus of claim71, wherein at least a portion of the micro channel is configured withan internal surface area between approximately 3e-11 m̂2 per linearmicron to 6e-10 m̂2 per linear micron.
 77. The apparatus of claim 71,wherein the wall portion further comprises a coating material depositedon a substrate.
 78. The apparatus of claim 77, wherein the substratecomprises copper.
 79. The apparatus of claim 77, wherein the coatingmaterial comprises tungsten.
 80. The apparatus of claim 71, wherein thewall portion is manufactured to be generally smooth.
 81. A method forheat exchange, comprising: providing a micro channel comprising a wallportion; providing a gas comprising a constituent particle; and inducinga flow of the gas adjacent to the wall portion; wherein the microchannel is configured to accommodate the flow of the gas in a firstdirection substantially perpendicular to a cross section of the microchannel; and wherein the wall portion and the constituent particle areconfigured such that collisions between the constituent particle and thewall portion are substantially specular; and wherein the wall portioncomprises at least a first wall portion, a second wall portion, a thirdwall portion, a first intermediate wall portion, and a secondintermediate wall portion; wherein a boundary of the first wall portionis contiguous with a first boundary of the first intermediate wallportion, a first boundary of the second wall portion is contiguous witha second boundary of the first intermediate wall portion, a secondboundary of the second wall portion is contiguous with a first boundaryof the second intermediate wall portion, and a boundary of the thirdwall portion is contiguous with a second boundary of the secondintermediate wall portion, such that the first wall portion, the firstintermediate wall portion, the second wall portion, the secondintermediate wall portion, and the third wall portion form a contiguousportion of the wall of the micro channel; wherein a first normal to thefirst wall portion is not parallel to a second normal to the second wallportion, and is also not parallel to a third normal to the third wallportion, and where the second normal is also not parallel to the thirdnormal; wherein an angle offset between the first normal and the secondnormal is less than 90 degrees, and is approximately the same as anangle offset between the second normal and the third normal; wherein aseparation between the first wall portion and the second wall portion isat least an integer N times a largest width of the micro channel overthat separation; and wherein the angle offset between the first normaland the second normal is less than M degrees where M equals N/10. 82.The method of claim 81, wherein N is selected from at least one of:twenty-five and fifty.
 83. The method of claim 81, wherein: the step ofproviding a micro channel comprising a wall portion comprises: providingthe wall portion at a first temperature at a first time; and wherein aportion of the fluid flows through the micro channel during a period oftime between the first time and a second time later than the first time;and wherein the wall portion exhibits a second temperature that is lessthan the first temperature at the second time.
 84. The method of claim81, wherein the gas comprises air.
 85. The method of claim 81, wherein apath of the micro channel is a spiral with an inner portion and an outerportion, where a radius if the outer portion is greater than a radius ofthe inner portion.
 86. The method of claim 81, further comprising,providing a heat exchange element conductively affixed to the wallportion.
 87. The method of claim 81, wherein at least a portion of themicro channel is configured with an internal surface area betweenapproximately 3e-11 m̂2 per linear micron to 6e-10 m ̂2 per linearmicron.
 88. The method of claim 81, wherein providing a micro channelcomprising a wall portion further comprises: depositing a material on asurface of the micro channel using at least one of: sputtering andevaporative deposition.
 89. The method of claim 88, wherein the surfaceis copper.
 90. The method of claim 88, wherein the material is tungsten.